The BD-9 was designed to be an Ultra-light aircraft. It was funded by a group in Philadelphia who had an excellent marketing record. The aircraft was designed to incorporate urethane foam molded skin, which was a unique design element that made the aircraft relatively lightweight and strong. The wings incorporated an 11 pound metal tubular spar that was from the BD-4 and milled to a taper. The results of this prototype were satisfactory at best even though it exceeded the empty weight by a small margin. A production version would’ve met the requirement, but the company it was built for decided against the extensive tooling costs it demanded.